alt Hacker NewsOr psychosomatic.
It's possible she believes that those items all trigger her migraines therefore her body gives her a migraine when she believes she's had one of her triggers.
A big tell would be her getting a migraine and blaming it on "hidden MSG" in a food item that doesn't have it.
Or her not getting migraine from foods that have MSG naturally but is never pointed out. Like tomatoes.
It's funny... reading this thread, I'm reminded of a friend of mine who indeed gets migraines from tomatoes. That was actually what she figured out first; the MSG connection came later.